Feature Request: Better 256 color detection

[rschristian]

The determination method for 256 color support is unfortunately quite conservative, as many terminals support it without having a name ending in -256color:

kolorist/src/index.ts

Lines 51 to 53 in a81083d

	TERM && TERM.endsWith('-256color')
	? SupportLevel.ansi256
	: SupportLevel.ansi;

For example, I use alacritty:

$ infocmp alacritty | grep colors
        colors#0x100

Alacritty does support True Color, but terminfo/ncurses is a bit silly and doesn't allow for multiple color specs in the same file. One would need need to look at alacritty-direct to get that info, but I digress.

I'm wondering if there's a non-awful way to get better detection here? I might take a look at other libraries and see what they're doing; my terminal is missing some much-needed color variety.

---

Edit: Well quick rabbit hole seems to indicate if you want to actually detect 256 support, you're out of luck; there's no reliable cross-platform method. However, $COLORTERM=truecolor seems somewhat viable as it's fairly popular across tools, and support for truecolor I believe grantees support for 256. Even Windows Terminal might support it.